Metal ion exchange by natural and modified zeolites

The lead and cadmium removal from wastewaters by natural and pretreatment zeolites was examined by using a batch-type method. The results demonstrated that the natural zeolites contained a complement of exchangeable Na, K and Ca ions but exposing them to 2 M NaCl solution at 22 and 70°C, respectively, converted them to a near homoionic state in Na-form. Lead and cadmium removal results using natural zeolites and treated zeolites showed that treatment improved both the exchange capacity and the removal efficiency. The influence of the temperature on the ion-exchange process was examined. It was found that the metal uptake was increased with increasing temperature during the ion-exchange process. Natural and modified zeolites remove toxic metals from waste waters.